Within the template, the builders section contains an array of all the builders
that Packer should use to generate a machine images for the template.

Builders are responsible for creating machines and generating images from them
for various platforms. For example, there are separate builders for EC2, VMware,
VirtualBox, etc. Packer comes with many builders by default, and can also be
extended to add new builders.

This documentation page will cover how to configure a builder in a template. The
specific configuration options available for each builder, however, must be
referenced from the documentation for that specific builder.

A single builder definition maps to exactly one
build. A builder definition is a
JSON object that requires at least a type key. The type is the name of the
builder that will be used to create a machine image for the build.

In addition to the type, other keys configure the builder itself. For example,
the AWS builder requires an access_key, secret_key, and some other settings.
These are placed directly within the builder definition.

An example builder definition is shown below, in this case configuring the AWS
builder:

Each build in Packer has a name. By default, the name is just the name of the
builder being used. In general, this is good enough. Names only serve as an
indicator in the output of what is happening. If you want, however, you can
specify a custom name using the name key within the builder definition.

This is particularly useful if you have multiple builds defined that use the
same underlying builder. In this case, you must specify a name for at least one
of them since the names must be unique.